This invention relates to a waste processing apparatus, a waste recovery system and a liquid container used in these, and particularly to for example an apparatus for dissolving discarded foam polystyrene, a system for recovering discarded foam polystyrene and a container used in these.
Foam polystyrene (so-called foam styrol, or EPS) moldings are used in large quantities in packing of home electrical products and AV (Audio Visual) appliances and the like. Foam polystyrene has merits such as that it has excellent impact absorbency, it can easily be processed into any shape, it is cheap and it has a clean appearance.
However, because on the other hand it has drawbacks such as that when disposed of by incineration it produces high temperature heat and shortens the life of the incinerator and also produces a strong offensive smell and that it does not decompose in soil when buried, with the shift toward environmental protection and resource-saving of recent years the use of foam polystyrene in large quantities has come to be seen as questionable.
In this connection, as a substitute material for foam polystyrene, pulp mold materials manufactured by recycling milk cartons, cardboard boxes and newspaper paper and the like have started to be used to some extent. However, whereas foam polystyrene exhibits excellent impact absorbency due to elasticity of its own, because pulp mold materials derive their shock-absorbing quality from paper being processed into a corrugated shape there is a limit to their strength and buffering performance and dispersion in their characteristics is also large.
Therefore, with respect to general packed products, and particularly large products such as refrigerators, washing machines and televisions, for the time being there is no alternative but to use foam polystyrene as a main packing material. Accordingly, recovering foam polystyrene moldings and recycling them has been being tried.
However, at present the recovery rate of foam polystyrene moldings is extremely low compared to that of paper. The main reason for this is that whereas there are many businesses collecting old paper such as newspapers and magazines and also the price of such paper is stable, foam polystyrene is extremely bulky for its weight, having an apparent specific gravity of about 0.02, and consequently carrying and storing it require a lot of space and it does not meet its recovery cost.
Although equipment for melting foam polystyrene moldings by heating them and making them into blocks has been introduced in some factories and other large facilities, introducing this kind of equipment in a wider field including general points of distribution such as shops and in homes and the like is not easy when cost, installation space and the production of offensive smells which accompanies thermal decomposition of polystyrene are considered. Also, because the molecular weight of the polystyrene molecules in the polystyrene blocks obtained is greatly decreased as a result of thermal decomposition, it is difficult to reuse the polystyrene.
Methods of recycling foam polystyrene moldings by means other than heating have also been used. One such method is that of dissolving foam polystyrene in an organic solvent to shrink its volume and then recovering the foam polystyrene by evaporating the organic solvent. In this method, because thermal processing is not carried out, the molecular weight of the polystyrene molecules is not reduced and the polystyrene can be reused.
In this kind of foam polystyrene processing method, when dissolving the used foam polystyrene in the organic solvent, it is necessary to supply unused organic solvent to the processing apparatus (an apparatus for dissolving the foam polystyrene and thereby reducing its volume) and receive a produced foam polystyrene solution and supply it to a recycling (recovery) system.
However, in the related art, because usually the container for supplying the unused organic solvent and the container for receiving the produced solution have been different dedicated containers and have been differently installed with respect to the processing apparatus, supply and discharge have been carried out with the amounts of liquid supplied and discharged being managed in units of a different fixed quantity in the case of each of these respective containers. Therefore, because it is necessary to carry out fitting and removal of each type of container with respect to the processing apparatus independently and management and carrying of the liquids must also be carried out separately, the ease of operation and the efficiency of the system have been poor and control of the concentration of the produced solution has tended to be inadequate. All the more so because foam polystyrene solution is viscous, not obtaining a solution of a fixed concentration (viscosity) at all times can have an adverse affect on the recycling (recovery) operation.
In the related art, as containers for holding liquids, containers such as the tin can 130A made of tin-plated steel sheet (so-called blik) shown in FIG. 1 and the polypropylene tank 130B shown in FIG. 2 have been widely used. Since these containers each have an opening 131A, 131B (covered by caps 132A, 132B in FIG. 1 and FIG. 2) in one location in the top of the container only, carrying out the above-mentioned dissolving of foam polystyrene moldings out in the way shown in FIG. 3 is conceivable.
FIG. 3 is a schematic sectional view of a foam polystyrene dissolving apparatus 121. A solvent 17 (for example limonene) is supplied to this dissolving apparatus 121 from a container 130 (for example the tin can 130A), and a stirring impeller 133 is disposed so as to be immersed in this solvent. Foam polystyrene moldings are broken up into small pieces 16 in advance and fed into the solvent through an opening 122, and while being stirred together with the solvent by the stirring impeller 133 dissolve in this solvent and become a polystyrene solution 18.
A solution discharge pipe 127 in which a valve 128 is disposed is connected to the bottom of the polystyrene dissolving apparatus 121 facing downward. A part 127a of the solution discharge pipe 127 below the valve 128 bends in two places and is rotatable as shown with the arrows between the position shown with broken lines and the position shown with solid lines. Also, a solvent supply pipe 129 is connected to the top of the polystyrene dissolving apparatus 121, and a pump 172 is disposed in the solvent supply pipe 129. A part 129a below the pump 172 bends in two places and is rotatable as shown with the arrows between the position shown with broken lines and the position shown with solid lines.
The state shown with solid lines in FIG. 3 is the state of the apparatus when polystyrene solution 18 produced in the polystyrene dissolving apparatus 121 is fed into the container 130. The part 127a of the solution discharge pipe 127 below the valve 128 is inserted into the opening 131 in the container 130, the valve 128 is opened and the polystyrene solution 18 is fed into the container 130 from the polystyrene dissolving apparatus 121.
To supply the solvent 17 to the polystyrene dissolving apparatus 121, the part 127a of the solution discharge pipe 127 is removed from the container 130 and positioned as shown with broken lines. Then, with solvent 17 in the container 130, the lower part 129a of the solvent supply pipe is inserted into the container opening 131 as shown with broken lines, the pump 172 is driven and the solvent 17 is transferred from the container 130 into the polystyrene dissolving apparatus.
Because the opening 131 is only provided in one location on the container 130, on every changeover between receiving of polystyrene solution 18 into the container 130 from the polystyrene dissolving apparatus 121 and supplying of solvent 17 from the container 130 into the polystyrene dissolving apparatus 121 it is necessary to interchange the discharge pipe lower part 127a and the solvent supply pipe lower part 129a in the opening 131.
To do this, for example, with the respective pipes in the positions shown with solid lines in FIG. 3 the valve 128 is closed, the container 130 is lowered and the discharge pipe lower part 127a is removed from the opening 131 and rotated to the position shown with broken lines and then the supply pipe lower part 129a is rotated to the position shown with broken lines and inserted into the opening 131 by the container 130 being raised again. Consequently, a large space is required for the pipes. Even when flexible hoses are used instead of the pipes described above, it is necessary to swing the hoses around and a large space is still necessary.
Furthermore, when feeding polystyrene solution 18 whose viscosity has become high from the polystyrene dissolving apparatus 121 into the container 130, because the opening 131 is small it is not possible to make the discharge pipe lower part 127a large in diameter, and the transfer takes time. It is notable in this connection that when d-limonene is used as the solvent, because a polystyrene solution of 30% concentration shows a high viscosity of 10,000 cps, with a small opening 131 it is not possible to transfer the solution into the container 130 smoothly.
For reasons of the kind described above, a container 130 of the related art is not satisfactory for use in processing foam polystyrene waste.
Also, recently, the kind of container shown in FIG. 4 has been developed and has gradually started to spread as a more suitable container, but to discharge a solution 18 held inside the container it is necessary to take off caps of a charging opening 84 and a discharging opening 85 and then tip the container and discharge the solution as shown in the drawing. This is also the same in the cases of the tin can 130A shown in FIG. 1 and the polypropylene tank 130B shown in FIG. 2; the discharging operation requires considerable effort, and particularly in the case of a highly viscous solution, because the discharging takes time, an inordinate amount of exertion is required.
With the container of FIG. 4, as shown in FIG. 5, it is possible to fit a strainer pipe 87 to the discharging opening 85 every time and discharge the solution 18 by sucking it out with a pump 86, but the efficiency of the operation is poor and it is necessary to separately make a strainer pipe which can be fitted to the discharging opening 85.
Although as described above systems for recovering and recycling discarded foam polystyrene moldings have started to operate, consideration has not been given to shapes and standards of containers for holding solutions most suited to liquid transfer and processing apparatuses, and the actual situation is that few proposals for making recycling efficient have been made.